The orthopedic wound is one of worst wound because it is usually deep towards bone surface. It necessitates cutting of the skin, subcutaneous tissues, and all the muscle layers down to the bone. Therefore, it is associated with many complications such as ugly skin scar, delayed healing, wasting of the limb, post-operative infection, and/or functional loss due to damage of vital structures like blood vessels or nerves.
All tissues of human body, except bone, heal by different degrees of fibrosis. The bone is the only tissue/structure that is not allowed to heal, except by bone similar to original one. Healing of a bone fracture with some degree of fibrosis is considered as a pathological process. It is clinically presented as either non-union or delayed union according to the amount of fibrous tissues. If a little amount of fibrous tissues is associated with healing, it is called as delayed union. If a large amount of fibrous tissues is associated with healing, it is called non-union, which usually necessitates surgical intervention. The effect of presence of fibrous tissues on bone healing is a tendency to fracture again.
A bone's function is to support all other structures so it is needed to be strong tissue and any area of fibrosis acts as a weak point subsequently, concentrating the stress to that point resulting in a re-fracture with minimal trauma. This phenomenon is known biomechanically as a stress raiser. Bone has two main properties that differentiate it from all other tissues in the human body. First, it has the largest number of mesenchymal cells (MSCs) in the bone marrow. These cells have the capacity to repair the damaged tissues with new ones similar to the original surrounding structure. This is the basis of stem cells injection for repairing of the tissues. Since 2009, it is well established that these MSCs are present in a dormant state around the blood vessels in all human tissues. The second property is that bone has a piezo-electric characteristics, e.g., compressing a living bone will produce electrical current of approximately 10−14 volts. This piezo-electrical property is fundamental for both bone maintenance and healing of a bone fracture. The electrical current acts as a method of cell-to-cell communications for new bone formation proportional to the amount of the mechanical stress. In other words, the higher mechanical stress on the bone, the higher the electrical charge produced. This action results in stimulation of more cells causing more new bone formation. The reverse is also true. In other words, it is both a proportional and quantitative process.
Recent research, in case of bone fracture, showed that this electrical charge stimulates dormant MSCs to be converted to bone cells Moreover, the site of fracture acts as a focusing site of the mechanical stresses which further enhance the stimulation of MSCs to become bone cells (osteoblasts which will become mature osteocytes). These cells are responsible of healing without fibrous tissues because the healing process is generated by MSCs not by fibroblast like other tissues.
To sum up, bone is unique tissue for the following reasons. First, it has the highest number of MSCs relative to other tissues (where the MSCs are present only around blood vessels). Being a piezo-electrical material, bone is capable of stimulating dormant MSCs. A fracture in a bone is the site of focused mechanical stresses. Those stresses are also able to stimulate MSCs, since MSCs are very sensitive to mechanical stimuli. Therefore, MSCs have double stimulants, namely, electrical and mechanical ones. The above reasons are responsible for the normal bone healing without fibrous tissues formation, because healing is done with MSCs.
Heretofore wounds to tissue other than bone have not exhibited the same response of healing as a bone injury. Thus, wounds particularly severe wounds, like orthopedic wounds, are frequently slow to heal and result in substantial fibrosis formation. The so-called “soft tissue healing law” is, perhaps, one of the most important paradigms in soft tissue healing and clearly denotes that the speed of the healing process is inversely proportional to the amount of the fibrous tissue formation. As such, there is a continuous and progressive need for faster healing of soft tissue wounds with less fibrous tissues. Such a result is desirable for both cosmetic and functional reasons, e.g., to regain the shape and function of any organ to its baseline condition just before it became wounded.
Moreover, the healing process is enhanced by an increased blood supply and the local molecular energy production, while it is inhibited by presence of infection and/or extensive tissue damage. In accordance with the soft tissue healing law, reducing the amount of fibrosis to a minimum enables the healing process to be indirectly increased to highest level.
Thus, the need exists for devices and methods for facilitating the rapid healing of wounds other than bone (e.g., soft tissue wounds of skin, muscle, tendon, etc.) with minimal, if any, fibrosis.
The subject invention addresses that need.